The present invention relates generally to a cassette holder in a recording and reproducing apparatus for a magnetic tape cassette which includes a sliding shutter which covers an opening or openings in the underside of a cassette casing. More specifically, the invention relates to a cassette holder having a mechanism for unlocking a lock for the sliding shutter. Still more particularly, the invention relates to a lock release mechanism for a sliding shutter on a tape cassette which is active both upon insertion of a cassette into, and ejection from, a cassette hold so that the shutter members may be locked, and released, both in its opened and closed positions.
In recent years, various types of recording and reproducing apparatus have been developed to convert analog signals, such as audio signals and the like, into digital signals, e.g. PCM signals, which are then recorded on and reproduced from magnetic tape serving as a recording medium. Some of these apparatuses employ rotary heads in order to achieve a relatively high recording density. A recording and reproducing apparatus specifically designed to record and reproduce PCM signals and employing a rotary head will be referred to as "PCM recorder" throughout the disclosure. As is known, a PCM recorder first pulls a loop of a magnetic tape out through a front opening of the tape cassette and winds the tape around a rotary drum accommodating the rotary head. When the tape is so located, the recording and reproducing is performed. In such digital recording and reproducing systems, oily deposits, such as fingerprints or the like, and/or dust adhering to the tape surface may cause a dropout of reproduced signals.
Various approaches have been tried to protect the magnetic recording medium. For example, a closure lid may be used to retractably cover the front end opening of the cassette, through which the tape is extracted for access by a rotary head. That closure lid is held closed while the tape is not in use and is moved to an open position when the cassette is inserted into the PCM recorder. With this earlier approach, a drawback may be encountered when the closure lid is unintentionally or accidentally opened, exposing the tape to oily fingerprints, dust and so forth while it is not in use. A locking mechanism which can conveniently lock the closure lid in its open and closed positions was proposed to resolve this problem.
Such a magnetic tape cassette which has a tape-protective pivotal lid has been disclosed in the U.S. Pat. No. 3,980,255, issued on Sept. 14, 1976, to Akio Serizawa and assigned to the assignee of the present invention. In the disclosure, the magnetic tape cassette for a magnetic recording and/or reproducing apparatus has a housing with an opening through which the tape can be withdrawn from the cassette housing for the recording and reproduction of signals thereon, as by one or more rotary heads. A lid is provided to normally close the housing opening when the cassette is not in use, thereby to protect the tape from damage. The lid is associated with a latch mechanism for locking the lid in its closed position, and this latch mechanism can be released by inserting the cassette into a cassette holder.
The magnetic tape cassette disclosed in the U.S. patent application Ser. No. 678,813, filed on Mar. 14, 1985 by Hiroshi Meguro, now U.S. Pat. No. 4,572,461 and assigned to the assignee of the present invention, has a sliding closure or shutter for closing a lower opening which allows entry of a loading device and a tape reel drive of the recording and reproducing apparatus. This sliding closure also is movable between open and close positions. The sliding shutter is associated with a lock mechanism which locks in it both its open and its closed positions.
In order to enable a recording and reproducing apparatus to handle the aforementioned type of magnetic tape cassette, there must be a mechanism or device for releasing the locking mechanism so that the sliding shutter may move from its closed position to the open position and back. Thus, it was a problem to provide such a lock release mechanism which is able to smoothly release the shutter member from either or both its locked-closed position or its locked-open position.